preg_replace() : pattern search and replace

$string=" Welcome to html  & HTML section";
$string=preg_replace("/html/","MySQL",$string);
echo $string;

Output

Welcome to MySQL & HTML section

Syntax

preg_replace('search_string','replace_string','main_string',limit,count);

Search_string:Enter the pattern of search string. This can be an array.
replace_string: If search string is found then this string ( replace_string ) is to be replaced.
main_string:This is our main string on which search will applied and replaced with replace string.
Limit :(optional ) We can specify how many times or occurrence of search to be replaced. It can be set to -1 for unlimited search and replace.
Count: ( optional )Returns the variable storing number of times search and replace is used within the string.

Example

<?Php
$string=" Welcome to plus2et.com , you can read html, php , jquery & HTML here";
$string=preg_replace("/html/","MySQL",$string);
echo $string;
?>

Output is here

Welcome to plus2et.com , you can read MySQL, php , jquery & HTML here

Note that we could change only html , not HTML . This is a case sensitive search and replace. To make it case in sensitive we have to add one i after the string delimiters.

$string=preg_replace("/html/i","MySQL",$string);

Now it is not case sensitive and both occurrence of the string HTML & html will be replaced with MySQL

Delimiters

To mark the starting and ending of the string we have used delimiters, in above case we used / as delimiters. However we can use any non-alphanumeric, non-backslash, non-whitespace character. Here is a list of commonly used delimiters to create patterns for searching.

Forward slash / , hash sign #, tildes ~

Counting Number of Replacements

We have one optional count variable which stores the number of replacements done by preg_replace().

<?Php
$string=" Welcome to plus2et.com , you can read html, php , jquery & HTML here";
$string=preg_replace("#html#i","MySQL",$string,-1,$count);
echo $string;
echo "<br>Total replacement done : $count ";
?>

Output is here

Welcome to plus2et.com , you can read MySQL, php , jquery & MySQL here
Total replacement done : 2

If you are dynamically building a query by taking different conditions connected by AND operator then this code is useful as you can replace the first occurrence of AND with a WHERE to complete your query.

$sql=preg_replace("/AND/","WHERE",$sql,1);

String Functions ucfirst(): First char to upper case str_replace(): String replace Counting Sub string inside a string

Subhendu Mohapatra

Author & Instructor at plus2net

I write and maintain practical tutorials on Python, PHP, SQL, JavaScript, HTML, jQuery, and web development at plus2net. The tutorials focus on clear explanations, working examples, and code that readers can test and adapt while learning.

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preg_replace() string pattern search and replacment

Syntax

Example

Delimiters

Counting Number of Replacements

Subhendu Mohapatra